JP3115206B2 - Arc sensor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an arc sensor device effective for gas shielded metal arc (GMA) welding.

[0002]

2. Description of the Related Art In recent years, in automatic arc welding, a torch is made to perform a periodic motion such as a swinging operation or a rotating operation, and the center axis of the torch is constantly adjusted by a signal obtained from a change in welding current. An arc sensor that performs welding by being positioned near the center of a circle is widely used.

As a specific conventional method of controlling an arc sensor for periodically moving a torch, Japanese Patent Publication No. 53-11502 is disclosed.
It was disclosed and practically used, but as the frequency of the periodic motion becomes higher, the sensor can be used with higher performance by using the welding voltage than by using the welding current disclosed in Japanese Patent Publication No. 53-11502. I understand. A conventional method using a welding voltage in the arc sensor control will be described with reference to FIGS.

FIG. 5 is a side view showing a welding state of arc welding to which conventional arc sensor control is applied. In FIG. 5, reference numerals 2a and 2b denote workpieces, M denotes a groove, and a central portion thereof is indicated by a chain line N. The welding tip 7 is inserted into the groove M, a welding wire 8 is sent out from the welding tip 7, and an arc is generated between the welding tips 2a and 2b during welding. As the welding torch (not shown) makes a periodic movement, the welding tip 7 fixed to the welding torch moves from 7a to 7b, then to 7a, 7c and then to 7a.

When the center of the periodic movement of the welding tip 7 passes through the central portion N of the groove M as shown in FIG. 5A, the welding voltage changes as shown in FIG. Welding tip 7 is 7a
The position becomes the welding voltage p of FIG. 6 (a), become s, the welding voltage of p ₁ back to 7a in the back and r, 7c of the position q, also the position of 7a at the position of 7b.

Next, when the center of the periodic movement of the welding tip is shifted upward from the center N of the groove M as shown in FIG. 5B, the welding voltage is changed as shown in FIG. Changes to
On the other hand, when it is shifted downward, the time axis in FIG. 6B is read as r, q as s, r as p, and s as q.

[0007] upper and lower half cycle of the welding voltage arc by integrating each (FIG. 6 (a), the inter-p-r and between r-p ₁ in FIG. 6 (b)), compare the top and bottom of the integral value By doing so, it is possible to detect at which position of the groove M the center of the periodic motion is located, thereby correcting the trajectory so that the center is always located at the center N or is shifted from the center by a set amount. Control becomes possible.

[0008]

However, in the above-mentioned conventional arc sensor, the output of the welding power source is mainly C at a constant voltage.
It is an ideal condition of O ₂ welding and MAG welding,
The actual welding voltage waveform does not change smoothly as shown in FIG. 6, but may change smoothly or change greatly due to reasons such as arc short-circuiting, fluctuations in wire feed, or periodic movement. . At that time, the conventional control method has a problem that a large error is generated as a result of calculating the relative position, and the trajectory meanders, or the trajectory following ability is reduced.

The present invention solves the above-mentioned conventional problems, and provides an arc sensor device capable of accurately detecting the relative position between a welding torch and a workpiece in gas metal arc (GMA) welding. The purpose is to:

[0010]

In order to achieve the above object, an arc sensor device according to the present invention comprises an arc voltage detector for detecting a voltage between a welding torch that moves periodically and a workpiece.
The set change rate is compared with the time change rate of the welding voltage detected by the arc voltage detector, and it is determined that the time change rate of the welding voltage is significantly changed from the set change rate ,
At the same time, the time change is faster and
When the welding voltage value is small,
Instantaneous change determiner to determine and detect the phase of periodic motion
A phase detector, wherein the arc sensor detects the arc voltage.
Of the welding voltage detected by the
Removed the section that was determined to be changing instantaneously
From the welding voltage, taking into account the output of the phase detector,
It specializes in detecting the relative position between the welding torch and the workpiece.
It shall be the butterfly.

[0011]

According to the present invention, the arc sensor can accurately determine the position of the welding torch between the welding torch and the workpiece by considering the output of the phase detector based on the voltage signal obtained by removing the voltage signal determined to be changing instantaneously. The relative position can be detected.
In addition, the left and right positions in the traveling direction of the workpiece and the welding torch can also be detected from the left voltage average value and the right voltage average value in the traveling direction of the welding torch.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
This will be described with reference to FIG. The same components as those described in the conventional example are denoted by the same reference numerals.

FIG. 1 is a block diagram of an arc sensor device according to one embodiment of the present invention. As shown in FIG. 1, in a gas shielded metal arc welding machine, an arc sensor device includes an arc voltage detector 3 that detects a voltage between a welding torch 1 and a workpiece 2 that make a periodic motion, and a set change rate. Is compared with the time rate of change of the welding voltage detected by the arc voltage detector 3, and it is determined that the welding voltage has changed significantly from the set change rate, and at the same time, the time change is earlier and the change rate is faster than the set time. The arc sensor 6 includes an instantaneous change determiner 4 that determines that the change rate is smaller than a set change rate, and a phase detector 5 that detects the phase of the periodic motion. The relative position between the welding torch 1 and the workpiece 2 is detected by taking into account the output of the phase detector 5 from the welding voltage excluding the section in which the instantaneous change is determined by the determiner 4. It is configured to.

FIG. 2 is a perspective view showing a weaving state of the welding tip during arc welding. In FIG.
Reference numerals 2a and 2b denote welded objects, respectively, forming a downward lap joint. A is a welding line, and indicates a boundary where the workpieces 2a and 2b overlap. Reference numeral 7 denotes a welding tip, which is fixed to a welding torch (not shown). Numeral 8 denotes a welding wire, which is fed from the center of the welding tip 7, generates an arc between the welding objects 2a and 2b and melts during welding, and welds the welding objects 2a and 2b. Then, as the welding torch (not shown) makes a periodic motion called weaving, the center axis B of the welding tip 7 is moved to the workpieces 2a, 2a.
b on the draw projection line C (p-q-r- s-p 1).

An arc sensor device in gas shielded metal arc welding (CO ₂ welding) in which the welding torch makes a periodic motion called weaving will be described. In this embodiment, the posture of the welding torch is when the welding tip 7 is welded to the workpiece 2a at a target angle of 45 degrees, and one cycle of movement is 20 ms.

If the center of the periodic motion of the welding tip is off the center of the groove and the arc state is relatively stable (in the case of FIG. 6B in the conventional example), the welding voltage is shown in FIG. As in Pattern A of No. 3, the pattern becomes relatively smooth, and there is no problem with the conventional method (the period is 0 to 20 ms).

However, when the welding wire is completely short-circuited to the workpiece, the pattern B shown in FIG.
s), the welding voltage is low (0 to 10 V) for a long time (around 5 ms), and the welding current is large, 300 to 50.
It jumps to 0 A, and at this time, it is difficult to employ it as a sensor signal because the characteristics of the sensor (the relationship between welding current and welding voltage) greatly change.

This embodiment is improved when the welding voltage is relatively small (1 to 10 V) and fluctuates for a short period (up to 4 ms) as shown in pattern C (period is 40 to 60 ms) in FIG. (Where the fluctuating period is between 40 and
It is around 50 ms within 60 ms). Pattern C in FIG.
, The welding current and welding voltage are set at the position p in FIG. 2 when the time is 40 ms, and at the position q when the time is 45 ms.
When ms is the position of r, the position of s when the 55 ms, when the 60ms respectively correspond to the position of the p _1. At this time, the time change rate (differential value) of the welding voltage is calculated, and it is determined that the change starts to change more than the set value (about 2 V / ms) and that the rapid change ends within the set time (about 4 ms). The instantaneous change determiner 4 determines that the welding voltage is instantaneously changing (48 to 51 ms for the welding voltage in FIG. 3), and the arc sensor 6 removes the welding voltage data during the instantaneous change from the sensor signal. ,
Taking into account the output of the phase detector 5, the relative position between the welding torch 1 and the workpiece 2 is detected. As a result, it is possible to distinguish the change in voltage due to the work to be welded and the change in welding voltage due to arc short-circuiting, fluctuations in wire feed, or for periodic movement, etc., and accurately measure the change in voltage due to the work to be welded. The accuracy of the sensor can be improved.

Further, as described above, it is possible to use no data when the welding voltage changes instantaneously.
As described above, the voltage value at which the welding voltage starts to change instantaneously and the voltage value at which the welding voltage ends are interpolated (linear interpolation: dotted line in the figure) and can be used as data of the arc sensor.

From the welding voltage data from which the instantaneously changed voltage has been removed, it can be used for detecting the left and right positions in the traveling direction of the welding torch. In general, a time-moving average value of the welding current (the period is 50 to 300 ms) is used in the front-rear direction (downward direction) of the welding torch.

Further, from the difference between the average value of the welding voltage on the left side and the average value of the welding voltage on the right side in the traveling direction during the periodic motion, it is possible to detect the position in the left and right direction in the traveling direction of the welding torch. . Generally, control is performed so that this difference voltage becomes a voltage (offset voltage) set in advance. If the absolute value of this offset voltage is small, it will be closer to the center of the joint, and if it is larger, it will deviate from the center of the joint, and the welding bead position can be set.

[0022]

As described above, according to the present invention, an arc voltage detector for detecting a voltage between a welding torch that moves periodically and an object to be welded, a set rate of change, and an arc voltage detected by the arc voltage detector. Compared with the time rate of change of the welding voltage.
Is determined, and the time change is also earlier than the set time.
Instantaneously when the changed welding voltage value is small
An instantaneous change determiner that determines that
It has a phase detector for detecting the phase, and the arc sensor
Of the welding voltage detected by the arc voltage detector.
Areas that are determined to be changing instantaneously by the change determiner
From the welding voltage with the gap removed, the output of the phase detector
Taking into account the relative position between the welding torch and the workpiece
In the gas shielded metal arc welding, the center of the periodic motion of the welding torch or the joint of the workpiece to be welded can be accurately detected because the relative position between the welding torch and the workpiece can be accurately detected. This provides an excellent effect that the trajectory control can be performed so as to reach the set position.

[Brief description of the drawings]

FIG. 1 is a block diagram of an arc sensor device according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a weaving state of a welding tip in the arc sensor device.

FIG. 3 is a diagram showing an example of a welding current and a welding voltage when a welding tip is periodically moved in the arc sensor device. Pattern A is a case where the welding voltage is relatively smooth. Pattern C is when the welding voltage changes instantaneously

FIG. 4 is a diagram showing an example of interpolation when the welding voltage changes instantaneously in the arc sensor device.

5A is a side view showing a welding state when the center axis of the conventional weaving operation is located at the center of the groove; FIG. 5B is a side view showing the center axis of the conventional weaving operation at the center of the groove; Side view showing the welding state when it is off the part

FIG. 6 (a) is a waveform diagram of a welding current when the central axis of the conventional weaving operation is located at the center of the groove; FIG. 6 (b) is the central axis of the conventional weaving operation where the central axis is the groove; Waveform diagram of welding current when deviated from

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Welding torch 2 Workpiece 3 Arc voltage detector 4 Instantaneous change judgment unit 5 Phase detector 6 Arc sensor

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B23K 9/127

Claims (4)

(57) [Claims] 1. An arc voltage detector for detecting a voltage between a welding torch and a workpiece to be periodically moved, and a set change rate and a time change rate of a welding voltage detected by the arc voltage detector are compared. Time change of the welding voltage from the set change rate.
Determines that rate changes significantly earlier than the time set is changed at the same time time, and the value of the changed welding voltage
An instantaneous change determiner for determining that the instantaneous change is being performed when it is small; and a phase detector for detecting the phase of the periodic motion, wherein the arc sensor detects the instantaneous change of the welding voltage detected by the arc voltage detector. From the welding voltage excluding the section where it is determined that the instantaneous change is being performed by the determiner,
An arc sensor device for detecting a relative position between a welding torch and a workpiece in consideration of an output of the phase detector. 2. The arc sensor device according to claim 1, wherein the welding voltage at the start and end of the section determined to be in an instantaneous change by the instantaneous change determiner is interpolated and used as the welding voltage. . 3. The method according to claim 1, wherein the welding voltage from which the section in which the instantaneous change is determined by the instantaneous change determiner is removed is used to detect the position of the welding torch in the left and right directions. The arc sensor device according to any one of the preceding claims. 4. An average value of a left voltage and a right voltage in a traveling direction of a welding torch during a periodic motion among welding voltages excluding a section determined to be in an instantaneous change by an instantaneous change determiner. 2. The arc sensor device according to claim 1, wherein the difference is used to detect the position of the welding torch in the left and right directions in the traveling direction.